The present invention relates to a process for producing an impermeable or substantially impermeable electrode, for example, electrolytic capacitors, supercapacitors or batteries.
It is known in the field of electrolytic capacitors to use metal foils as cathodes. Therein the metal foils are etched chemically or electrochemically. The etching penetrates into the material body of the metal foil whereby the surface and, thus, the specific capacitance, of the. foil is increased. Due to the etching, the electric resistance, for example of an aluminum foil, in comparison to a non-etched foil, is increased by a factor which is a function of the quantity of the metal removed during the. etching process. In addition, the metal foil loses mechanical strength. The natural oxidation which takes place with this treatment yields a capacitance which is a function of the dielectric constant of the metal itself and the treatment performed on the metal foil.
In contrast, according to the present invention the desired capacitance is attained through the deposition of graphite. In this way neither the electric resistance nor the mechanical strength of the metal foil are impaired.